The present invention relates to a coordinates detection apparatus which detects coordinates of a point specified on the surface of a panel such as a touch panel.
There have been known various types of coordinates detection apparatus used, for instance, for touch panel. For example, such an apparatus is disclosed in Japanese Patent Laid-Open Publication No. HEI 9-91094. In the apparatus disclosed in this application, two optical units each having a light-emitter and a light-receiver are provided at different positions on the border of the surface of the touch panel, and further a reflection section which reflects a light emitted from the light-emitter in the direction from where the light was emitted on the border of the surface.
As mentioned above, the conventional coordinates detection apparatus has two optical units and a reflection section. Light from the light-emitter is projected parallel to the surface of the panel in the form of a fan. The light is reflected by the reflection section in the direction from where the light was emitted, that is, towards the light-emitter. The reflected light is received by the light-receiver. When a user touches a point on the surface of the panel, with a finger or the like, then the light passing through this point is interrupted. Therefore, there occur places in each of the light-receivers which do not receive the reflected light. Accordingly, from the position of such places in the light-receivers it is possible to calculate the coordinates of the point where the finger of the like had touched the surface of the panel.
The coordinates detection apparatus disclosed in Japanese Patent Laid-Open Publication No. HEI 9-91094 has following disadvantages. The optic axis of the light-emitter and the light-receiver have an angle between them. Therefore, the light-emitter and light-receiver must be located with a specified space therebetween. This makes it difficult to reduce a size of the optical unit which comprises the light-emitter and the light-receiver.
Furthermore, a lens is provided in front of the light-receiver in the path of the reflected light. This lens forms an image on the light-receiver. Because the optic axis of the light-emitter and the light-receiver have an angle between them, there is a problem that, the center of the light projected from the light-emitter and diffused in the form of a fan is offset from the center of the lens provided in front of the light-receiver. Resultantly, there is a disadvantage that the precision in detection of the coordinates is low.
It is an object of the present invention to provide a coordinates detection apparatus which makes it possible to reduce a size of the optical unit used therein.
It is another object of the present invention to provide a coordinates detection apparatus which insures high precision in detection of the coordinates.
According to the coordinates detection apparatus of one aspect of the present invention, optic axis of the light-emitter and the light-receiver are coincident to each other. Therefore, the light-emitter and light-receiver can be located at positions close to each other.
Further, the half mirror is located on the optic axes of the light-emitter and light-receiver. Therefore, the light-emitter and light-receiver can be located at any positions by making use of this half mirror.
Further, the light-emitter, diffusion lens, read lens, and half mirror are mounted in one frame. Therefore, the size of the optical unit can be reduced.
Further, a central point of emission of light diffused by the lens and a principal point of the read lens are coincident to each other.
Further, the optical unit has an optical adjustment mechanism for the light-emitter and light-receiver. Therefore, the light-emitter and light-receiver in each optical unit can be adjusted discretely.
Further, the optical unit is located at a position close to the display surface. Therefore, optic axes of the light-emitter and the light-receiver can be located at a position close to the display surface.
Further, there is provided a mounting position adjustment mechanism for adjusting a mounting position of the optical unit. Therefore, precision in detection of the coordinates can be improved by adjusting a mounting position of the optical unit.
Other objects and features of this invention will become apparent from the following description with reference to the accompanying drawings.